1. Field of the Invention
The present invention relates to a composite material-stiffened panel to be applied to a wing and a tail assembly of an aircraft and a manufacturing method thereof.
2. Description of the Related Art
As a conventional stiffened panel, stiffened panels shown in FIGS. 1 through 4 are known.
A stiffened panel 10 shown in FIG. 1 is formed in such a manner that a skin 11 and a stiffener 12 are manufactured according to respective shapes, and they are bound to each other by a fastener 13 (rivet or the like).
A stiffened panel 10a shown in FIG. 2 is formed in such a manner that a skin 11a and a stiffener 12a are manufactured according to respective shapes, and they are bonded by an adhesive 14.
A stiffened panel 10b shown in FIG. 3 is formed in such a manner that a metal thick plate 15 shown by a dotted line is machined to be a stiffened panel (solid line).
A stiffened panel 10c shown in FIG. 4 is formed in such a manner that a composite material is formed into a stiffened plate by molding a skin 17 and a stiffener 18 integrally by means of a molding tool 16.
The method of manufacturing a stiffened panel by binding a skin and a stiffener by means of a fastener requires molding of the skin and the stiffener and provision of a positioning tool, thus resulting in high cost. Other problems are strict fastener design requirements (hole-edge distance and skin thickness for no sharp edges to a countersink) and reducing of fatigue strength due to a fastener-hole stress concentration.
The method of manufacturing a stiffened panel by bonding a skin and a stiffener by means of an adhesive requires molding of the skin and the stiffener, a pre-bonding process for the skin and the stiffener, positioning the skin and the stiffener, and provision of a pressurized holding tool for bonding, thus the cost becomes high.
The method of manufacturing a stiffened panel by machining a thick metal plate by machine working has a problem that since much of the material is cut and discarded, resources are wasted, and a problem that as weight efficiency is heightened, the cost of machine working becomes higher.
The method of manufacturing a stiffened panel by means of integral molding of a composite material has a problem of high cost factors such as provision of a complex tool for an accurately and integrally molded shape and of pressurizing the entire surface and an increase in scrap risk.
In view of the problems discussed above, an object of the present invention is to provide a composite material-stiffened panel for enhanced bonding of a fiber-reinforced resin-composite skin and a stiffener and a manufacturing method thereof.
The present invention provides a composite material-stiffened panel including: a skin obtained by molding a fiber-reinforced resin-composite material into a flat skin; stiffeners arranged in rows on one surface of the skin; and a fiber-reinforced resin-composite material stitched on the skin and covering the stiffeners.
Moreover, the present invention provides a method of manufacturing a composite material-stiffened panel including the steps of: placing a first fabric material on a tool having a panel-shaped surface; placing stiffeners on the first fabric material; placing a second fabric material on the stiffeners so as to cover at least some of the stiffeners; reforming the second fabric material so as to match the shape of the stiffeners; stitching the reformed second fabric material on the first fabric material along edges of the stiffeners; covering all the materials with a bagging film for vacuum; infiltrating resin into the fabric materials by a RTM or a RFI method; and heating the infiltrated resin to be hardened.
Moreover, the present invention provides a method of manufacturing a composite material-stiffened panel including the steps of: placing a first fabric material on a tool having panel-shaped surface; placing a second fabric material on the first fabric material so as to be loosened in some places for stiffeners to be put through; putting the stiffeners through between the loosened second fabric material and the first fabric material; reforming the second fabric material so as to match the shape of the stiffeners; stitching the reformed second fabric material on the first fabric material along edges of the stiffeners; covering all the materials with a bagging film for vacuum; infiltrating resin into the first and second fabric materials by a RTM or a RFI method; and heating the infiltrated resin, to be hardened.